The glinting behaviour of USA 32 (88-078A)

The year 2009 has started with a period of frost, and hence clear skies. I observed on January 6 and 9 and this evening (the 11th), catching a batch of objects: Lacrosse 3, USA 32, and various NOSS duo's.

The image of USA 32 (88-078A, a SIGINT satellite launched in September 1988) of this evening very nicely shows the glinting behaviour of this satellite. Along the trail, small bright dots (= very short glints) can be seen at regular intervals. They are indicated by the downward pointing arrows in the image (a 10.05 second exposure taken with my Canon EOS 450D and EF 50/2.5 Macro lens at F2.8):

(click image to enlarge)

Below is a brightness profile derived from the pixel brightness along the trail. The same peaks as indicated by the arrows in the photograph, show up well and are labelled A to H:

(click image to enlarge)

Analyzing the position of the glints, shows the following sequence:

1) a series of 4 or more glints at a regular 1.20 second interval;
2) followed by 2.0 seconds of no, or much less bright glints;
3) followed again by 4 or more glints at a regular 1.20 second interval.